The present invention relates to a toner cartridge detachably fitted to a developing unit employed in an imaging device and the like utilizing the so-called electrophotographic system, and used for supplying toner stored therein to the developing device. More particularly the invention relates to a toner cartridge capable of reducing the space occupied by an empty toner cartridge after use and therefore decreasing the size of an imaging device by minimizing a dead space.
Conventionally, electronic copying machines, laser printers and the like are well known as imaging device utilizing the electrophotographic system.
The Electrophotographic system is a technique comprising the steps of employing photoconductive material, i.e., photosensitive material, to make a photoconductive drum, exposing to the photoconductive drum light to from a latent image the surface of the photoconductive drum uniformly being charged with electricity, adhering toner to the latent image to develop a visible image, i.e., toner image, transferring the toner image to a recording sheet and simultaneously fixing the toner image thereto by means of a fixing unit, and discharging the recording sheet on which the visible image corresponding to the latent image is formed.
The developing unit for performing the developing operation is generally formed as a unit based on its function. The unit is arranged to provide the surface of the photoconductive drum with toner via developing rollers or the like by charging the toner stored in a toner chamber.
However, as toner is consumed during the above developing operation, it has to be supplied to the toner chamber, in accordance with the volume consumed. Although toner can simply be supplied to the toner chamber directly from a toner container, it tends to fly apart or float in air and may stain hands and clothing.
Due to this problem, as illustrated in FIG. 1, a toner cartridge 30 containing toner is fitted to a developing unit 20. The toner cartridge 30 is made of rigid material such as plastic and the like and formed into a container detachable from the developing unit 20. In many cases where toner is supplemented, the used cartridge, i.e., the empty cartridge, fitted to the developing unit 20 is removed before being replaced with a new cartridge to supply the toner contained in the new cartridge to the developing unit 20. In other words, the toner cartridge 30 is normally fitted into a supply gate led to the developing unit 20 and the toner cartridge 30 after the contents are emptied out therefrom is used to function as a cover for the toner supply gate.
With the above arrangement, however, the toner cartridge 30, though empty after the contents are emptied into the developing unit 20, still remains installed in the developing unit 20 as if it were loaded with toner. As a result, the space occupied by the toner cartridge 30 becomes so-called dead space, thus providing an obstacle to reducing the size of the imaging device.